LOVOO invitation codes are special voucher codes shaped like this: "xxx-xxxx-xxx". They are distributed as special offers and can only be redeemed within the LOVOO app.
In order to redeem an invitation code, please open your profile settings. You will find "Redeem voucher code" at the top. Enter your personal code and click on "Check" followed by "Redeem now". Please note that it may be necessary to restart your app so that all changes may be applied correctly and all Premium features may be used.